1. Field of the Invention
The present invention relates to a rotatable shaft assembling method, a rotatable shaft assembly and an electric motor having the rotatable shaft assembly.
2. Description of Related Art
For example, Japanese Unexamined Patent Publication No. JP2002-115716A discloses an electric motor having a speed reducing mechanism. Specifically, a worm gear mechanism, which serves as the speed reducing mechanism, is received in a gear housing, and a worm shaft (a rotatable shaft) of the worm gear mechanism is connected to a motor shaft, which is rotated upon driving of a motor main body. The worm shaft is rotatably supported by the gear housing through two bearings (metal plain bearings), which are spaced from each other by a predetermined distance. In the assembling method of the above worm shaft, the bearings are respectively installed into the gear housing, and then the worm shaft is installed into the gear housing and is supported by the bearings. Furthermore, thrust adjustment of the worm shaft is executed after assembling of the gear housing to the motor main body.
However, in the case of the previous assembling method of the worm shaft, the step of installing the first bearing to the gear housing and the subsequent step of installing the second bearing to the gear housing are executed first, and then the step of installing the worm shaft is executed. In such a case, the individual components are separately installed to cause an increase in the number of assembling steps. Furthermore, the assembling requires two kinds of jigs, i.e., the jig for installing the bearing and the jig for installing the worm shaft.